'\" te
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.\" Portions Copyright (c) 2007, Sun Microsystems, Inc. All Rights Reserved.
.TH CPL_COMPLETE_WORD 3TECLA "January 18, 2020"
.SH NAME
cpl_complete_word, cfc_file_start, cfc_literal_escapes, cfc_set_check_fn,
cpl_add_completion, cpl_file_completions, cpl_last_error, cpl_list_completions,
cpl_recall_matches, cpl_record_error, del_CplFileConf, cpl_check_exe,
del_WordCompletion, new_CplFileConf, new_WordCompletion \- look up possible
completions for a word
.SH SYNOPSIS
.nf
cc [ \fIflag\fR\&.\|.\|. ] \fIfile\fR\&.\|.\|. \fB-ltecla\fR [ \fIlibrary\fR\&.\|.\|. ]
#include <stdio.h>
#include <libtecla.h>

\fBWordCompletion *\fR\fBnew_WordCompletion\fR(\fBvoid\fR);
.fi

.LP
.nf
\fBWordCompletion *\fR\fBdel_WordCompletion\fR(\fBWordCompletion *\fR\fIcpl\fR);
.fi

.LP
.nf
\fBCPL_MATCH_FN\fR(\fBcpl_file_completions\fR);
.fi

.LP
.nf
\fBCplFileConf *\fR\fBnew_CplFileConf\fR(\fBvoid\fR);
.fi

.LP
.nf
\fBvoid\fR \fBcfc_file_start\fR(\fB(CplFileConf *\fR\fIcfc\fR, \fBint\fR \fIstart_index\fR);
.fi

.LP
.nf
\fBvoid\fR \fBcfc_literal_escapes\fR(\fBCplFileConf *\fR\fIcfc\fR, \fBint\fR \fIliteral\fR);
.fi

.LP
.nf
\fBvoid\fR \fBcfc_set_check_fn\fR(\fBCplFileConf *\fR\fIcfc\fR, \fBCplCheckFn *\fR\fIchk_fn\fR,
     \fBvoid *\fR\fIchk_data\fR);
.fi

.LP
.nf
\fBCPL_CHECK_FN\fR(\fBcpl_check_exe\fR);
.fi

.LP
.nf
\fBCplFileConf *\fR\fBdel_CplFileConf\fR(\fBCplFileConf *\fR\fIcfc\fR);
.fi

.LP
.nf
\fBCplMatches *\fR\fBcpl_complete_word\fR(\fBWordCompletion *\fR\fIcpl\fR, \fBconst char *\fR\fIline\fR,
     \fBint\fR \fIword_end\fR, \fBvoid *\fR\fIdata\fR, \fBCplMatchFn *\fR\fImatch_fn\fR);
.fi

.LP
.nf
\fBCplMatches *\fR\fBcpl_recall_matches\fR(\fBWordCompletion *\fR\fIcpl\fR);
.fi

.LP
.nf
\fBint\fR \fBcpl_list_completions\fR(\fBCplMatches *\fR\fIresult\fR, \fBFILE *\fR\fIfp\fR, \fBint\fR \fIterm_width\fR);
.fi

.LP
.nf
\fBint\fR \fBcpl_add_completion\fR(\fBWordCompletion *\fR\fIcpl\fR, \fBconst char *\fR\fIline\fR,
     \fBint\fR \fIword_start\fR, \fBint\fR \fIword_end\fR, \fBconst char *\fR\fIsuffix\fR,
     \fBconst char *\fR\fItype_suffix\fR, \fBconst char *\fR\fIcont_suffix\fR);
.fi

.LP
.nf
\fBvoid\fR \fBcpl_record_error\fR(\fBWordCompletion *\fR\fIcpl\fR, \fBconst char *\fR\fIerrmsg\fR);
.fi

.LP
.nf
\fBconst char *\fR\fBcpl_last_error\fR(\fBWordCompletion *\fR\fIcpl\fR);
.fi

.SH DESCRIPTION
The \fBcpl_complete_word()\fR function is part of the \fBlibtecla\fR(3LIB)
library. It is usually called behind the scenes by \fBgl_get_line\fR(3TECLA),
but can also be called separately.
.sp
.LP
Given an input line containing an incomplete word to be completed, it calls a
user-provided callback function (or the provided file-completion callback
function) to look up all possible completion suffixes for that word. The
callback function is expected to look backward in the line, starting from the
specified cursor position, to find the start of the word to be completed, then
to look up all possible completions of that word and record them, one at a
time, by calling \fBcpl_add_completion()\fR.
.sp
.LP
The \fBnew_WordCompletion()\fR function creates the resources used by the
\fBcpl_complete_word()\fR function. In particular, it maintains the memory that
is used to return the results of calling \fBcpl_complete_word()\fR.
.sp
.LP
The \fBdel_WordCompletion()\fR function deletes the resources that were
returned by a previous call to \fBnew_WordCompletion()\fR. It always returns
\fINULL\fR (that is, a deleted object). It takes no action if the \fIcpl\fR
argument is \fINULL\fR.
.sp
.LP
The callback functions that look up possible completions should be defined with
the \fBCPL_MATCH_FN()\fR macro, which is defined in <\fBlibtecla.h\fR>.
Functions of this type are called by \fBcpl_complete_word()\fR, and all of the
arguments of the callback are those that were passed to said function. In
particular, the \fIline\fR argument contains the input line containing the word
to be completed, and \fIword_end\fR is the index of the character that follows
the last character of the incomplete word within this string.  The callback is
expected to look backwards from \fIword_end\fR for the start of the incomplete
word. What constitutes the start of a word clearly depends on the application,
so it makes sense for the callback to take on this responsibility. For example,
the builtin filename completion function looks backwards until it encounters an
unescaped space or the start of the line. Having found the start of the word,
the callback should then lookup all possible completions of this word, and
record each completion with separate calls to \fBcpl_add_completion()\fR. If
the callback needs access to an application-specific symbol table, it can pass
it and any other data that it needs using the \fIdata\fR argument. This removes
any need for global variables.
.sp
.LP
The callback function should return 0 if no errors occur. On failure it should
return 1 and register a terse description of the error by calling
\fBcpl_record_error()\fR.
.sp
.LP
The last error message recorded by calling \fBcpl_record_error()\fR can
subsequently be queried by calling \fBcpl_last_error()\fR.
.sp
.LP
The \fBcpl_add_completion()\fR function is called zero or more times by the
completion callback function to record each possible completion in the
specified \fBWordCompletion\fR object. These completions are subsequently
returned by \fBcpl_complete_word()\fR. The \fIcpl\fR, \fIline\fR, and
\fIword_end\fR arguments should be those that were passed to the callback
function. The \fIword_start\fR argument should be the index within the input
line string of the start of the word that is being completed. This should equal
\fIword_end\fR if a zero-length string is being completed. The \fIsuffix\fR
argument is the string that would have to be appended to the incomplete word to
complete it. If this needs any quoting (for example, the addition of
backslashes before special characters) to be valid within the displayed input
line, this should be included. A copy of the suffix string is allocated
internally, so there is no need to maintain your copy of the string after
\fBcpl_add_completion()\fR returns.
.sp
.LP
In the array of possible completions that the \fBcpl_complete_word()\fR
function returns, the suffix recorded by \fBcpl_add_completion()\fR is listed
along with the concatenation of this suffix with the word that lies between
\fIword_start\fR and \fIword_end\fR in the input line.
.sp
.LP
The \fItype_suffix\fR argument specifies an optional string to be appended to
the completion if it is displayed as part of a list of completions by
\fIcpl_list_completions\fR. The intention is that this indicates to the user the
type of each completion. For example, the file completion function places a
directory separator after completions that are directories, to indicate their
nature to the user. Similarly, if the completion were a function, you could
indicate this to the user by setting \fItype_suffix\fR to "()". Note that the
\fItype_suffix\fR string is not copied, so if the argument is not a literal
string between speech marks, be sure that the string remains valid for at least
as long as the results of \fBcpl_complete_word()\fR are needed.
.sp
.LP
The \fIcont_suffix\fR argument is a continuation suffix to append to the
completed word in the input line if this is the only completion. This is
something that is not part of the completion itself, but that gives the user an
indication about how they might continue to extend the token. For example, the
file-completion callback function adds a directory separator if the completed
word is a directory. If the completed word were a function name, you could
similarly aid the user by arranging for an open parenthesis to be appended.
.sp
.LP
The \fBcpl_complete_word()\fR function is normally called behind the scenes by
\fBgl_get_line\fR(3TECLA), but can also be called separately if you separately
allocate a \fBWordCompletion\fR object. It performs word completion, as
described at the beginning of this section. Its first argument is a resource
object previously returned by \fBnew_WordCompletion()\fR. The \fIline\fR
argument is the input line string, containing the word to be completed. The
\fIword_end\fR argument contains the index of the character in the input line,
that just follows the last character of the word to be completed. When called
by \fBgl_get_line()\fR, this is the character over which the user pressed TAB.
The \fImatch_fn\fR argument is the function pointer of the callback function
which will lookup possible completions of the word, as described above, and the
\fIdata\fR argument provides a way for the application to pass arbitrary data
to the callback function.
.sp
.LP
If no errors occur, the \fBcpl_complete_word()\fR function returns a pointer to
a \fBCplMatches\fR container, as defined below. This container is allocated as
part of the \fIcpl\fR object that was passed to \fBcpl_complete_word()\fR, and
will thus change on each call which uses the same \fIcpl\fR argument.
.sp
.in +2
.nf
typedef struct {
    char *completion;        /* A matching completion */
                             /* string */
    char *suffix;            /* The part of the */
                             /* completion string which */
                             /* would have to be */
                             /* appended to complete the */
                             /* original word. */
    const char *type_suffix; /* A suffix to be added when */
                             /* listing completions, to */
                             /* indicate the type of the */
                             /* completion. */
} CplMatch;

typedef struct {
    char *suffix;            /* The common initial part */
                             /* of all of the completion */
                             /* suffixes. */
    const char *cont_suffix; /* Optional continuation */
                             /* string to be appended to */
                             /* the sole completion when */
                             /* nmatch==1. */
    CplMatch *matches;       /* The array of possible */
                             /* completion strings, */
                             /* sorted into lexical */
                             /* order. */
    int nmatch;              /* The number of elements in */
                             /* the above matches[] */
                             /* array. */
} CplMatches;
.fi
.in -2

.sp
.LP
If an error occurs during completion, \fBcpl_complete_word()\fR returns
\fINULL\fR. A description of the error can be acquired by calling the
\fBcpl_last_error()\fR function.
.sp
.LP
The \fBcpl_last_error()\fR function returns a terse description of the error
which occurred on the last call to \fBcpl_complete_word()\fR or
\fBcpl_add_completion()\fR.
.sp
.LP
As a convenience, the return value of the last call to
\fBcpl_complete_word()\fR can be recalled at a later time by calling
\fBcpl_recall_matches()\fR. If \fBcpl_complete_word()\fR returned \fINULL\fR,
so will \fBcpl_recall_matches()\fR.
.sp
.LP
When the \fBcpl_complete_word()\fR function returns multiple possible
completions, the \fBcpl_list_completions()\fR function can be called upon to
list them, suitably arranged across the available width of the terminal. It
arranges for the displayed columns of completions to all have the same width,
set by the longest completion. It also appends the \fItype_suffix\fR strings
that were recorded with each completion, thus indicating their types to the
user.
.SS "Builtin Filename completion Callback"
By default the \fBgl_get_line()\fR function passes the
\fBCPL_MATCH_FN\fR(\fBcps_file_completions\fR) completion callback function to
\fBcpl_complete_word()\fR. This function can also be used separately, either by
sending it to \fBcpl_complete_word()\fR, or by calling it directly from your
own completion callback function.
.sp
.in +2
.nf
#define CPL_MATCH_FN(fn) int (fn)(WordCompletion *cpl, \e
                              void *data, const char *line, \e
                              int word_end)

typedef CPL_MATCH_FN(CplMatchFn);

CPL_MATCH_FN(cpl_file_completions);
.fi
.in -2

.sp
.LP
Certain aspects of the behavior of this callback can be changed via its
\fIdata\fR argument. If you are happy with its default behavior you can pass
\fINULL\fR in this argument. Otherwise it should be a pointer to a
\fBCplFileConf\fR object, previously allocated by calling
\fBnew_CplFileConf()\fR.
.sp
.LP
\fBCplFileConf\fR objects encapsulate the configuration parameters of
\fBcpl_file_completions()\fR. These parameters, which start out with default
values, can be changed by calling the accessor functions described below.
.sp
.LP
By default, the \fBcpl_file_completions()\fR callback function searches
backwards for the start of the filename being completed, looking for the first
unescaped space or the start of the input line. If you wish to specify a
different location, call \fBcfc_file_start()\fR with the index at which the
filename starts in the input line. Passing \fIstart_index\fR=-1 reenables the
default behavior.
.sp
.LP
By default, when \fBcpl_file_completions()\fR looks at a filename in the input
line, each lone backslash in the input line is interpreted as being a special
character which removes any special significance of the character which follows
it, such as a space which should be taken as part of the filename rather than
delimiting the start of the filename. These backslashes are thus ignored while
looking for completions, and subsequently added before spaces, tabs and literal
backslashes in the list of completions. To have unescaped backslashes treated
as normal characters, call \fBcfc_literal_escapes()\fR with a non-zero value in
its \fIliteral\fR argument.
.sp
.LP
By default, \fBcpl_file_completions()\fR reports all files whose names start
with the prefix that is being completed. If you only want a selected subset of
these files to be reported in the list of completions, you can arrange this by
providing a callback function which takes the full pathname of a file, and
returns 0 if the file should be ignored, or 1 if the file should be included in
the list of completions. To register such a function for use by
\fBcpl_file_completions()\fR, call \fBcfc_set_check_fn()\fR, and pass it a
pointer to the function, together with a pointer to any data that you would
like passed to this callback whenever it is called. Your callback can make its
decisions based on any property of the file, such as the filename itself,
whether the file is readable, writable or executable, or even based on what the
file contains.
.sp
.in +2
.nf
#define CPL_CHECK_FN(fn) int (fn)(void *data, \e
                                       const char *pathname)

typedef CPL_CHECK_FN(CplCheckFn);

void cfc_set_check_fn(CplFileConf *cfc, CplCheckFn *chk_fn, \e
                                             void *chk_data);
.fi
.in -2

.sp
.LP
The \fBcpl_check_exe()\fR function is a provided callback of the above type,
for use with \fBcpl_file_completions()\fR. It returns non-zero if the filename
that it is given represents a normal file that the user has permission to
execute. You could use this to have \fBcpl_file_completions()\fR only list
completions of executable files.
.sp
.LP
When you have finished with a \fBCplFileConf\fR variable, you can pass it to
the \fBdel_CplFileConf()\fR destructor function to reclaim its memory.
.SS "Thread Safety"
It is safe to use the facilities of this module in multiple threads, provided
that each thread uses a separately allocated \fBWordCompletion\fR object. In
other words, if two threads want to do word completion, they should each call
\fBnew_WordCompletion()\fR to allocate their own completion objects.
.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Evolving
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.BR libtecla (3LIB),
.BR ef_expand_file (3TECLA),
.BR gl_get_line (3TECLA),
.BR pca_lookup_file (3TECLA),
.BR attributes (7)
